Rechargeable Stimulators in Deep Brain Stimulation for Obsessive-Compulsive Disorder: A Prospective Interventional Cohort Study.

BACKGROUND: From 1999 onwards, deep brain stimulation (DBS) has been proposed as an alternative to capsulotomy in refractory cases of obsessive-compulsive disorder (OCD). Although rechargeable implantable pulse generators (rIPGs) have been used extensively in DBS for movement disorders, there are no reports on rIPGs in patients with a psychiatric DBS indication, and even possible objections to their use. OBJECTIVE: We aim to evaluate rIPGs in OCD in terms of effectiveness, applicability, safety, and need for IPG replacement. METHODS: In this prospective before-after study recruiting from 2007 until 2012, OCD patients requiring at least one IPG replacement per 18 months were proposed to have a rIPG implanted at the next IPG depletion. OCD severity was the primary outcome. Ten patients were analyzed. RESULTS: Psychiatric symptoms and global functioning remained stable in the two years after as compared to the two years before rIPG implantation. Over the same period, the prescribed OCD medication doses did not increase and the DBS stimulation parameters were largely unaltered. Until the end of the follow-up (mean 4¾ years; maximum seven years), the DBS-related surgery frequency decreased and there were no rIPG replacements. During the first few weeks after implantation, two patients obsessively checked the rIPG, but afterwards there were no signs of compulsively checking or recharging the rIPG. Two patients experienced rIPG overdischarges (five occurrences in total). CONCLUSIONS: This is the first report on rIPGs in DBS for OCD patients. The use of rIPGs in this population appears to be effective, applicable, and safe and diminishes the need for IPG replacements.

Field Potential Oscillations in the Bed Nucleus of the Stria Terminalis Correlate with Compulsion in a Rat Model of Obsessive-Compulsive Disorder.

UNLABELLED: The bed nucleus of the stria terminalis (BNST) is implicated in anxiety and reward processing, both of which are associated with obsessive-compulsive disorder (OCD). Specific neuronal groups in the BNST related to anxiety and reward have been identified, but quantitative data about the information carried by local field potential (LFP) signals in this area during obsession/compulsion are lacking. Here we investigate the BNST LFP in the schedule-induced polydipsia, an animal model of OCD. We implanted electrodes bilaterally in the BNST and random control brain regions in 32 male Wistar rats, and recorded corresponding LFP during compulsive and noncompulsive behavior. We first applied high-frequency (100 Hz) electrical stimulation through the implanted electrodes and analyzed its effects on compulsive behavior. We then performed time-frequency analysis of LFPs and statistically compared the normalized power of δ (1-4 Hz), θ (4-8 Hz), α (8-12 Hz), ß (12-30 Hz), and lower γ (30-45 Hz) bands between different groups. Our data showed that the normalized δ, ß, and γ powers in the right BNST were specifically correlated with compulsive behaviors. δ and γ oscillations increased and decreased during the initiation phase of compulsion, respectively, whereas ß increased after compulsion stopped. Moreover, the effect of BNST electrical stimulation, in terms of suppression of compulsion, was significantly correlated with the percentage change of these bands during compulsion. Our research reveals potential biomarkers and underlying neurophysiological mechanisms of compulsion and warrants further assessment of the use of LFP for closed-loop neuromodulation in OCD. SIGNIFICANCE STATEMENT: Although specific neuronal groups in the bed nucleus of the stria terminalis (BNST) related to anxiety and reward circuitries have been identified, psychopathological information carried by local field potentials in the BNST has not yet been described. We discovered that normalized powers of the right BNST δ, ß, and γ oscillations were highly correlated with compulsion. Specifically, δ and γ oscillations increased and decreased during the initiation phase of compulsion, respectively, whereas ß increased after compulsion stopped. Such correlations were not found in other parts of the brain during compulsion, or in the BNST during noncompulsive behavior. Current findings reveal real-time neurophysiological biomarkers of compulsion and warrant further assessment of the use of local field potentials for closed-loop neuromodulation for OCD.

Small animal PET imaging of the type 1 cannabinoid receptor in a rodent model for anorexia nervosa.

PURPOSE: Several lines of evidence strongly implicate a dysfunctional endocannabinoid system (ECS) in eating disorders. Using [(18)F]MK-9470 and small animal positron emission tomography (PET), we investigated for the first time cerebral changes in type 1 cannabinoid (CB1) receptor binding in vivo in the activity-based rat model of anorexia (ABA), in comparison to distinct motor- and food-related control conditions and in relation to gender and behavioural variables. METHODS: In total, experiments were conducted on 80 Wistar rats (23 male and 57 female). Male rats were assigned to the cross-sectional conditions: ABA (n = 12) and CONTROL (n = 11), whereas female rats were divided between two settings: (1) a cross-sectional design using ABA (n = 13), CONTROL (n = 9), and two extra control conditions for each of the variables manipulated in ABA, i.e. DIET (n = 8) and WHEEL (n = 9), and (2) a longitudinal one using ABA (n = 10) and CONTROL (n = 8) studied at baseline, during the model and upon recovery. The ABA group was subjected to food restriction in the presence of a running wheel, the DIET group to food restriction without wheel, the WHEEL group to a normal diet with wheel and CONTROL animals had a normal diet and no running wheel. Parametric CB1 receptor images of each group were spatially normalized to Paxinos space and analysed voxel-wise. RESULTS: In the ABA model, absolute [(18)F]MK-9470 binding was significantly increased in all cortical and subcortical brain areas as compared to control conditions (male +67 %; female >51%, all p cluster < 6.3×10(-6)) that normalized towards baseline values after weight gain. Additionally, relative [(18)F]MK-9470 binding was increased in the hippocampus, inferior colliculus and entorhinal cortex of female ABA (+4.6%; p cluster < 1.3×10(-6)), whereas no regional differences were observed in male subjects. Again, relative [(18)F]MK-9470 binding values normalized upon weight gain. CONCLUSION: These data point to a widespread transient disturbance of the endocannabinoid transmission, specifically for CB1 receptors in the ABA model. Our data also suggest (1) gender effects on regional CB1 receptor binding in the hippocampus and (2) add further proof to the validity of the ABA model to mimic aspects of human disease.

Micro-positron emission tomography imaging of rat brain metabolism during expression of contextual conditioning.

Using (18)F-fluorodeoxyglucose microPET imaging, we investigated the neurocircuitry of contextual anxiety versus control in awake, conditioned rats (n = 7-10 per group). In addition, we imaged a group expressing cued fear. Simultaneous measurements of startle amplitude and freezing time were used to assess conditioning. To the best of our knowledge, no neuroimaging studies in conditioned rats have been conducted thus far, although visualizing and quantifying the metabolism of the intact brain in behaving animals is clearly of interest. In addition, more insight into the neurocircuitry involved in contextual anxiety may stimulate the development of new treatments for anxiety disorders. Our main finding was hypermetabolism in a cluster comprising the bed nucleus of the stria terminalis (BST) in rats expressing contextual anxiety compared with controls. Analysis of a subset of rats showing the best behavioral results (n = 5 per subgroup) confirmed this finding. We also observed hypermetabolism in the same cluster in rats expressing contextual anxiety compared with rats expressing cued fear. Our results provide novel evidence for a role of the BST in the expression of contextual anxiety.

Resorbable scaffold based chronic neural electrode arrays.

We have developed a novel type of neural electrode array for future brain-machine interfaces (BMI) and neural implants requiring high resolution recording and stimulation on the surface of brain lesions or on the cortex. The devices differ on two points from commonly used thin film electrode arrays: first, the thin film backbone of the implant is exceptionally thin (down to 5 microns) and finely patterned into spring-like structures. This increases the flexibility of the electrode array and allows stretching and conforming better to a quasi spherical cavity surface. Second, the thin film backbone of the device is reinforced with a porous layer of resorbable chitosan. This design aims at minimal invasiveness and low mechanical irritation during prolonged use, while the chitosan matrix ensures the implant is stiff enough for practical handling during the implantation procedure and dissolves afterwards. Furthermore, the chitosan adds haemostatic and antiseptic properties to the implant and improves adhesion. In the article, the design and fabrication process are presented. In vitro and long term in vivo test results over a 12 month period are shown. By adopting the use of a resorbable scaffold-like material as main constituent of neural implants, the presented work opens up the possibility of applying tissue engineering techniques to further improve neural implant technology.

Contextual conditioning in rats as an animal model for generalized anxiety disorder.

Animal models of psychiatric disorders are important translational tools for exploring new treatment options and gaining more insight into the disease. Thus far, there is no systematically validated animal model for generalized anxiety disorder (GAD), a severely impairing and difficult-to-treat disease. In this review, we propose contextual conditioning (CC) as an animal model for GAD. We argue that this model has sufficient face validity (there are several symptom similarities), predictive validity (it responds to clinically effective treatments), and construct validity (the underlying mechanisms are comparable). Although the refinement and validation of an animal model is a never-ending process, we want to give a concise overview of the currently available evidence. We suggest that the CC model might be a valuable preclinical tool to enhance the development of new treatment strategies and our understanding of GAD.

Comparative study of the effects of electrical stimulation in the nucleus accumbens, the mediodorsal thalamic nucleus and the bed nucleus of the stria terminalis in rats with schedule-induced polydipsia.

In the schedule-induced polydipsia model, hungry rats receiving a food pellet every minute will display excessive drinking behaviour (compulsive behaviour). We aimed 1) to evaluate if electrical stimulation in the nucleus accumbens (N ACC), the mediodorsal thalamic nucleus (MD) or the bed nucleus of the stria terminalis (BST) can decrease water intake in the schedule-induced polydipsia model; 2) to compare water intake between these groups for different stimulation amplitudes; and 3) to compare the effect of low frequency (2 Hz) with high frequency (100 Hz) stimulation. Rats were randomly divided into four groups: electrode implanted in the 1) N ACC (n=7), 2) MD (n=8), 3) BST (n=8), or 4) a sham-operated control group (n=7). Postoperatively, each rat of group 1, 2 and 3 was randomly tested in the model using pulses with a frequency of 2 Hz and 100 Hz, each at an amplitude of 0.1, 0.2, 0.3, 0.4 and 0.5 mA, or without stimulation. Group 4 was tested 11 times without stimulation. Each day the rats were tested in random order. High-frequency electrical stimulation in all three brain areas decreased water intake significantly at an amplitude of 0.2 mA or higher, however, without differences between the brain areas. Based on these results, we expect a decrease in compulsions in patients suffering from treatment-resistant obsessive-compulsive disorder during electrical stimulation in the N ACC, the MD and the BST. However, we foresee no difference in energy consumption to decrease symptoms during electrical stimulation between these brain areas.

Electrical stimulation in the lateral hypothalamus in rats in the activity-based anorexia model.

OBJECT: One quarter of patients with anorexia nervosa have a poor outcome and continue to suffer chronically or die. Electrical brain stimulation may be of therapeutic benefit in some of these patients; however, the brain target for inducing symptom relief is unknown. In this study, the authors evaluated the effects of acute and chronic electrical stimulation in the lateral hypothalamus on food intake, locomotor activity, and survival time in rats in an activity-based anorexia model. METHODS: In an acute experiment, the authors electrically stimulated at 100 Hz and 0, 25, 50 and 75% of the maximal stimulation amplitude (that is, the amplitude leading to severe side effects) in the lateral hypothalamus on consecutive days during 4 test sessions in 10 rats and evaluated food intake and locomotor activity. In a chronic experiment, they compared food intake, wheel revolutions, and survival time between 6 rats that underwent electrical stimulation in the lateral hypothalamus (50% of maximal stimulation amplitude) and 8 rats that did not undergo stimulation. RESULTS: In the acute experiment, overall electrical stimulation (25, 50, and 75% combined) and stimulation at 75% of the maximal stimulation amplitude significantly decreased the locomotor activity. However, if the authors omitted results of 1 rat, in which the electrode tip was not located in the lateral hypothalamus on one side but rather in the supraoptic chiasm, the remaining results did not yield significance. No other differences were observed. CONCLUSIONS: When the findings of the current study are extrapolated to patients with anorexia nervosa, the authors do not expect major effects on symptoms with electrical stimulation at high frequency in the lateral hypothalamus.

Erratum: Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

This corrects the article DOI: 10.1038/srep09921.

Extracellular matrix proteins as temporary coating for thin-film neural implants.

OBJECTIVE: This study investigates the suitability of a thin sheet of extracellular matrix (ECM) proteins as a resorbable coating for temporarily reinforcing fragile or ultra-low stiffness thin-film neural implants to be placed on the brain, i.e. microelectrocorticographic (µECOG) implants. APPROACH: Thin-film polyimide-based electrode arrays were fabricated using lithographic methods. ECM was harvested from porcine tissue by a decellularization method and coated around the arrays. Mechanical tests and an in vivo experiment on rats were conducted, followed by a histological tissue study combined with a statistical equivalence test (confidence interval approach, 0.05 significance level) to compare the test group with an uncoated control group. MAIN RESULTS: After 3 months, no significant damage was found based on GFAP and NeuN staining of the relevant brain areas. SIGNIFICANCE: The study shows that ECM sheets are a suitable temporary coating for thin µECOG neural implants.

Quantitative analysis of motor evoked potentials in the neonatal lamb.

Evoking motor potentials are an objective assessment method for neuromotor function, yet this was to our knowledge never done in neonatal lambs. There is neither a method for standardized quantification of motor evoked potentials (MEPs). We first aimed to evaluate the feasibility of MEP recording in neonatal lambs and test its validity. Second we aimed to develop an algorithm for its quantification and test its reliability since manual input is required. We recorded myogenic MEPs after transcranial motor cortex stimulation in 6 lambs aged 1-2 days. MEPs were also measured in one lamb undergoing Neuro-Muscular Blockade (NMB) and another undergoing lumbar spinal cord (SC) transection, both serving as controls. We computed 5 parameters using a custom-made algorithm: motor threshold, latency, area-under-the-curve, peak-to-peak amplitude and duration. Intra- and inter-observer reliability was analyzed. MEPs could be easily recorded, disappearing after NMB and SC transection. The algorithm allowed for analysis, hence physiologic readings of the parameters in all 4 limbs of all lambs were obtained. Our method was shown to have high intra- and inter-observer ( ≥70%) reliability for latency, area-under-the-curve and peak-to-peak amplitude. These results suggest that standardized MEP recording and analysis in neonatal lambs is feasible, and can reliably assess neuromotor function.

Image-based in vivo assessment of targeting accuracy of stereotactic brain surgery in experimental rodent models.

Stereotactic neurosurgery is used in pre-clinical research of neurological and psychiatric disorders in experimental rat and mouse models to engraft a needle or electrode at a pre-defined location in the brain. However, inaccurate targeting may confound the results of such experiments. In contrast to the clinical practice, inaccurate targeting in rodents remains usually unnoticed until assessed by ex vivo end-point histology. We here propose a workflow for in vivo assessment of stereotactic targeting accuracy in small animal studies based on multi-modal post-operative imaging. The surgical trajectory in each individual animal is reconstructed in 3D from the physical implant imaged in post-operative CT and/or its trace as visible in post-operative MRI. By co-registering post-operative images of individual animals to a common stereotaxic template, targeting accuracy is quantified. Two commonly used neuromodulation regions were used as targets. Target localization errors showed not only variability, but also inaccuracy in targeting. Only about 30% of electrodes were within the subnucleus structure that was targeted and a-specific adverse effects were also noted. Shifting from invasive/subjective 2D histology towards objective in vivo 3D imaging-based assessment of targeting accuracy may benefit a more effective use of the experimental data by excluding off-target cases early in the study.

Anodal tDCS over the Primary Motor Cortex Facilitates Long-Term Memory Formation Reflecting Use-Dependent Plasticity.

Previous research suggests that anodal transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) modulates NMDA receptor dependent processes that mediate synaptic plasticity. Here we test this proposal by applying anodal versus sham tDCS while subjects practiced to flex the thumb as fast as possible (ballistic movements). Repetitive practice of this task has been shown to result in performance improvements that reflect use-dependent plasticity resulting from NMDA receptor mediated, long-term potentiation (LTP)-like processes. Using a double-blind within-subject cross-over design, subjects (n=14) participated either in an anodal or a sham tDCS session which were at least 3 months apart. Sham or anodal tDCS (1 mA) was applied for 20 min during motor practice and retention was tested 30 min, 24 hours and one week later. All subjects improved performance during each of the two sessions (p < 0.001) and learning gains were similar. Our main result is that long term retention performance (i.e. 1 week after practice) was significantly better when practice was performed with anodal tDCS than with sham tDCS (p < 0.001). This effect was large (Cohen's d=1.01) and all but one subject followed the group trend. Our data strongly suggest that anodal tDCS facilitates long-term memory formation reflecting use-dependent plasticity. Our results support the notion that anodal tDCS facilitates synaptic plasticity mediated by an LTP-like mechanism, which is in accordance with previous research.

Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation.

Effects of electrical stimulation or lesion in nucleus accumbens on the behaviour of rats in a T-maze after administration of 8-OH-DPAT or vehicle.

Electrical brain stimulation may be a therapeutic alternative for irreversible lesions in treatment-resistant patients with obsessive-compulsive disorder (OCD). We compared the effects of electrical stimulation and lesion in the nucleus accumbens (n acc) on the behaviour of rats in a model for OCD. Rats were tested for spontaneous alternation behaviour (AB) in a T-maze and assigned to four groups: an electrode implant group with stimulation 'ON' (stimON) or 'OFF' (stimOFF), a lesion or a sham group. Postoperatively, the number of arm visits and AB were tested after 8-hydroxy-2-(di-n-propylamino)-tetralin hydrobromide (8-OH-DPAT; 2 mg/kg) or saline administration. After 8-OH-DPAT administration, more arm visits were counted in the stimON (92.2%) and lesion groups (79.3%) than in both control groups (stimOFF 54.2; sham 61.2%). AB was significantly decreased in the stimON (10.5%) and lesion groups (10.2%) relative to the sham (22.0%) but not to the stimOFF group (14.7%). After saline administration, rats performed more arm visits in the stimON (81.5% non-significant) and lesion groups (93.6% significant) relative to the stimOFF (70.8%) and the sham groups (74.5%). No significant differences, however, were observed for AB. In conclusion, both treatments resulted in a decreased AB after 8-OH-DPAT administration (modelling an increase in compulsions) and more arm visits.

Electrical stimulation of the anterior limbs of the internal capsules in patients with severe obsessive-compulsive disorder: anecdotal reports.

Anterior capsular stimulation induces some improvement in severe treatment-resistant OCD patients. At this stage, not all stimulation-induced effects can be explained. The effects are a valuable source for further neurophysiologic and neuroanatomic research. It was reassuring that when the group of Drs Rasmussen, Greenberg, and Friehs in Providence and the group of Drs Rezai, Montgomery, and Malone in Cleveland started to operate on OCD patients using exactly the same technique, similar effects were seen in the patients. The authors still want to stress that anterior capsular stimulation remains investigational and needs optimization, especially to try to solve the problem of the short battery life of the stimulators.

Rethinking food anticipatory activity in the activity-based anorexia rat model.

When a rat is on a limited fixed-time food schedule with full access to a running wheel (activity-based anorexia model, ABA), its activity level will increase hours prior to the feeding period. This activity, called food-anticipatory activity (FAA), is a hypothesized parallel to the hyperactivity symptom in human anorexia nervosa. To investigate in depth the characteristics of FAA, we retrospectively analyzed the level of FAA and activities during other periods in ABA rats. To our surprise, rats with the most body weight loss have the lowest level of FAA, which contradicts the previously established link between FAA and the severity of ABA symptoms. On the contrary, our study shows that postprandial activities are more directly related to weight loss. We conclude that FAA alone may not be sufficient to reflect model severity, and activities during other periods may be of potential value in studies using ABA model.

Targeting bed nucleus of the stria terminalis for severe obsessive-compulsive disorder: more unexpected lead placement in obsessive-compulsive disorder than in surgery for movement disorders.

BACKGROUND: In preparation for a multicenter study, a protocol was written on how to perform surgical targeting of the bed nucleus of the stria terminalis, based on the lead implantation experience in patients with treatment-refractory obsessive-compulsive disorder (OCD) at the Universitaire Ziekenhuizen Leuven (UZ Leuven). When analyzing the postoperative images, we were struck by the fact that the difference between the postoperative position of the leads and the planned position seemed larger than expected. METHODS: The precision of targeting in four patients with severe OCD who received bilateral model 3391 leads (Medtronic) was compared with the precision of targeting in the last seven patients who underwent surgery at UZ Leuven for movement disorders (four with Parkinson disease and three with essential tremor; all received bilateral leads). Because the leads implanted in six of the seven patients with movement disorders were model 3387 leads (Medtronic), targeting precision was also analyzed in four patients with OCD in whom model 3387 leads were implanted in the same target as the other patients with OCD. RESULTS: In the patients with OCD, every implanted lead deviated at least 1.3 mm from its intended position in at least one of three directions (lateral, anteroposterior, and depth), whereas in the patients with movement disorders, the maximal deviation of any of all implanted leads was 1.3 mm. The deviations in lead placement were comparable in patients with OCD who received a model 3387 implant and patients who received a model 3391 implant. In the patients with OCD, all leads were implanted more posteriorly than planned. CONCLUSIONS: The cause of the posterior deviation could not be determined with certainty. The most likely cause was an increased mechanical resistance of the brain tissue along the trajectory when following the targeting protocol compared with the trajectories classically used for subthalamic nucleus or ventral intermediate nucleus of the thalamus stimulation.